Anaerobic Digestion Evidence
Availability and Gap Analysis
A s t r a t e g i c r e v i e w o f r e s e a r c h a n d a v a i l a b l e e v i d e n c e o n a n a e r o b i c d i g e s t i o n , w i t h a p r i o r i t i s e d a s s e s s m e n t o f g a p s a n d r e c o m m e n d a t i o n s f o r f u r t h e r w o r k
Report to Defra
Project Number WR1311
Paul Frith, Frith Resource Management Ltd
Dr Jane Gilbert, Eco Alternatives Ltd
This research was commissioned and funded by Defra. The views expressed reflect the research findings and the authors’ interpretation. The inclusion of or reference to any particular policy in this report should not be taken to imply that it has, or will be, endorsed by Defra. Recommendations for further research will be considered and may be followed by further action where appropriate.
This report is a summary of a rapid overview of evidence on completed and on-going research into anaerobic digestion of food and other waste e.g. paper, manures, crop residues and energy crops (however it was not limited to these feedstocks only). It has been conducted following the publication of Defra’s 2010 AD Framework Document, which sets the context for this study.
This report does not attempt to summarise all the available evidence on AD, as this would be an extremely large project. Instead it summarises key areas where evidence was found to be strong, partial or missing. Reference to select publications are made as part of an initial desk based data collation exercise, however, it is recognised that this is not intended to be comprehensive. Expert opinion from stakeholders, organisations and individuals has been sought to supplement the desk review.
In general, the evidence base was particularly strong in the following areas:
Process optimisation and characterisation – there is a large body of scientific evidence, as well as a number of dedicated web sites detailing process control and biogas optimisation;
Manure and energy crop digestion – these feedstocks are widely digested in the USA and Europe, hence they have been widely reported; and
Small-scale rural systems – which are aimed principally at developing countries, where operating standards may not meet UK legislative requirements (e.g. in respect of emissions).
In recent years, Defra, DECC and WRAP have commissioned research into a range of AD-related areas, including:
Food waste digestion, including process optimisation;
AD technologies and applications; and
Benefits of digestate application to soils, including market development.
Some of this evidence has been published, whilst some research projects were ongoing at the time of writing. However, in order to realise Defra’s vision for AD as outlined in the 2010 Framework Document, this study identified areas where further evidence is required. This report thus presents a prioritised assessment of the gaps where evidence is still needed, identifying whether initiatives are required in the short- or longer-term as well as indicating whether this work would be applied or requiring significant research innovation.
The evidence gaps identified within the analysis are categorised into 14 areas and summarised in Table 1. There are 23 specific actions that fall within these categories as defined within the report, and their respective importance is categorised as high, medium or low priority.
Table 1 – Evidence gaps identified with priority rankings
Gap Topic Identified
| Priority of the particular actionsto address these gaps*
| 1. Up-to-date, accurate information on the current size of theAD sector
| 2. Characterisation & Understanding of primarily food wastefeedstocks and digestion
| 3. Municipal interfaces with AD treatment
4. Financial: capital costs, operating costs and revenue
| High & Medium
| 5. Financing...
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